1. Field of the Invention
This invention relates to an optical device, for example, binoculars, and especially relates to a correcting mechanism which corrects a tremble of a focused image using correction optical systems.
2. Description of the Related Art
Conventionally, some binoculars, provided with a tremble correcting function which corrects a tremble of a focused image due to a hand tremble, are known. For example, in Japanese Patent Publication No. P2000-199862, a focused image tremble correcting device is disclosed. The device moves correction optical systems in two directions crossing at right angles on a plane perpendicular to the optical axes of the correction optical systems such that the focused image tremble is canceled.
In the device, the correction optical systems are held by a lateral-direction driving frame, and the lateral-direction driving frame is supported in an opening portion of the lengthwise-direction driving frame. Further, the device includes two direct-drive-actuators which move the driving frames. Each of the actuators has a motor and a shaft which converts a rotational movement of the motor to a liner movement using a lead screw. The lateral-direction actuator is supported by the lengthwise-direction driving frame.
Now, the movement of the correction optical systems in the lengthwise direction will be explained. The shaft of the lengthwise-direction direct-drive actuator extends in the lengthwise direction which approximately coincides with the vertical direction when the optical device is used in a usual position. The tip end of the shaft is abutted against a guide pin which is unitarily provided at a lower side of the frame. The frame is pulled upward by a coil spring, so that the guide pin is pressed against the tip end of the shaft from the lower side.
Accordingly, the guide pin and the frame are moved in the lengthwise direction in accordance with the movement of the shaft. The driving force of the shaft caused by the motor is set to a value which is necessary to press the lengthwise-direction driving frame downward. Namely, the driving force is set to a value obtained by subtracting the gravity of the lengthwise-direction driving frame, the lateral-direction driving frame, the lateral-direction actuator, and the correction optical systems, from the pulling force of the coil spring.
As described above, the pulling force of the coil spring is directed in the upward vertical direction, when the optical device is used in the usual position. However, as the direction of the pulling force varies in accordance with user""s holding way and pose, the direction of the pulling force does not always coincide with the upward vertical direction. For example, when the optical device is held upside down, the pulling force is directed in the downward vertical direction. Accordingly, the pulling force and the above-mentioned gravity act on the shaft, and the total force acting on the shaft becomes larger than the driving force of the shaft, so that there is the possibility that the motor might pull out.
Therefore, an object of the present invention is to prevent the motor from pulling out due to the position of the optical device, and to keep the shaft in a precise portion of the driving frame.
In accordance with an aspect of the present invention, there is provided a device for correcting tremble of a focused image comprising: a correction optical system for correcting a tremble of an optical axis of an optical device; a driving frame, holding the correction optical system, that can be moved in a predetermined direction on a plane perpendicular to the optical axis; a driving mechanism that includes a shaft, the central axis of which is parallel to the predetermined direction, and that drives linearly the shaft along the central axis; and a transmitting mechanism that transmits the linear movement of the shaft to the driving frame by supporting the shaft at the both ends of the shaft.
Accordingly, the linear movement of the shaft is transmitted to the driving frame. Therefore, no matter how the optical device is held, the driving mechanism, for example, a motor, is prevented from being pulled out and not working well due to an added load.
Preferably, the predetermined direction corresponds to the vertical direction when the optical device is held in a usual manner. Even if the position of the optical device is upside down, the driving frame can be accurately driven.
Preferably, the transmitting mechanism includes: two projecting portions that project from the driving frame along the optical axis so as to respectively face the corresponding ends of the shaft; and a pressing member, provided on at least one of the projecting portions, that supports the shaft at both ends of the shaft with another of the projecting portions.
Further, the projecting portions may work as a guide member which guide the driving frame in a predetermined direction or the moving direction of the driving frame. To put it concretely, two guide holes, the longitudinal axis of which extends in the predetermined direction, are provided in the optical device, and the projecting portions are respectively moved in the two guide holes, whereby the driving frame is moved, being guided in the predetermined direction.
Optionally, the driving mechanism may include a screw feeder mechanism that transmits the rotation of the motor to said shaft. Preferably, the ends of the shaft are in point-contact with the transmitting mechanism when the shaft linearly moves rotating by the screw feeder mechanism. Accordingly, a friction between the shaft and the transmitting mechanism is lowered, and a load added to the motor is reduced.
For example, the pressing member, which supports the shaft at both ends of the shaft with the projecting portions, includes: a case that is fixed on one of the projecting portions; a press pin that can be moved along the central axis of the shaft against the case; and a coil spring provided in the case, that urges the press pin along the central axis of the shaft. The tip end of the press pin is spherical and in contact with one end of the shaft at all times.
Further, optionally, the pressing member may be a set screw fixed on one of the projecting portions. A tip end of the set screw is formed spherical, and is in point-contact with one end of the shaft, so that the tip end presses the shaft along the axis of the shaft.
Furthermore, optionally, the pressing member may be a plunger fixed on the projecting portion. The plunger includes: a ball that is provided at a tip end of the plunger; a coil spring that urges the ball along the axis of the shaft.
Optionally, one of the end portions of the shaft is formed spherical, a plane portion perpendicular to the axis of the shaft is formed on the projecting portion, and the end portion is in contact with the plane portion at all times.
In accordance with another aspect of the present invention, there is provided an optical device comprising a correction mechanism for a tremble of a focused image. The correction mechanism corrects a tremble of an optical axis of the optical device by moving a correction optical system in a first and a second directions which cross at right angle on a plane perpendicular to an optical axis of the correction optical system. The correction mechanism comprises: a first driving frame which can be moved in the first direction, and on which an opening portion is formed; a first driving mechanism which includes a first shaft parallel to the first direction and which moves linearly the first shaft along its axis; a first transmitting mechanism which supports the first shaft at both ends of the first shaft, being fixed on the first driving frame, whereby a linear movement of the first shaft is transmitted to the first driving frame; a second driving frame which can be moved in the second direction and which holds the correction optical system; a second driving mechanism which includes a second shaft parallel to the second direction and which moves linearly the second shaft along its axis; and a second transmitting mechanism which supports the second shaft at both ends of the second shaft, being fixed on the second driving frame, whereby a linear movement of the second shaft is transmitted to the second driving frame. The second driving frame, the second driving mechanism, and the second transmitting mechanism are supported by the first driving frame.